1. Field of the Invention
The present invention relates to an immunoassay process for analyzing bloods or other compositions extracted from living bodies in the clinical examination, and more particularly to a simplified process for immunoassay wherein a dry analytical element (integral multi-layered analysis element) is used to diagnose immunologically the change in disease or the degree of disease or to identify the kind of the disease. The substance contained in blood or other compositions extracted from living bodies and analyzed by the process of this invention will be referred to as "analyte" throughout the specification and appended claims.
2. Related Art Statement
There has been known in the art a variety of immunoassay elements and immunoassay processes in which the so-called antigen-antibody reactions are utilized. The known examination elements include dry analytical elements, such as filter paper impregnated with a reagent, an integral multi-layered analysis element (hereinafter referred to as "multi-layered analysis element" in some portions of this specification) having a reagent layer and a porous spreading layer. However, the accuracies and sensitivities of these known dry-type immunoassay elements are unsatisfactory for practical applications, although they may be used through simple operations.
An example of the known immunoassay process, in which a dry analytical element is used, is a process wherein a slide described in Japanese Patent Laid-Open Publication No. 501144/1983 (WO 83/00391) is used. The slide contains a glass fiber filter sheet which serves as a porous layer. An antibody for the analyte antigen is immobilized on the glass fiber filter sheet. When serum containing the analyte antigen is spotted on the slide, the analyte antigen is bound to the immobilized antibody. An aqueous liquid containing a labelled antigen labelled with a fluorescent marker is then spotted on the sheet so that the labelled antigen is bound to the remaining immobilized antibody which has not been bound to the analyte antigen. The reaction zone of the sheet is rinsed with a rinsing liquid to wash off the excess labelled antigen in a radially outward direction to remove the free labelled antigen from the reaction zone (B/F separation is effected by this rinsing operation). The fluorescent light emitted from the marker in the labelled antigen-antibody complex, which is immobilized by the glass fibers in the reaction zone, is sensed to find the optical density thereof. The thus found datum is compared to a calibration curve to determine the quantity of the analyte antigen contained in the serum. This process is described in "NIPPON RINSHO KENSA JIDOKA GAKKAI-SHI" ("Journal of the Japanese Society of Automation of Clinical Examination"), 10(1), pages 57 to 60 (1985) and in "Clinical Chemistry", 28(9), pages 1894 to 1898 (1985), and applied for practical uses. This known process has a disadvantage in that a rinsing liquid must be supplied precisely to the very center of the reaction zone on the slide to effect B/F separation.